It depends on the group, if the DPS are able to deal decent amount of damage and the healer can handle it, then I see no issue with pulling alot of mobs, but if the dps are not able to deal enough damage or the healer has a hard time keeping you alive, then maybe its wise to dial down and pull small groups.

In the level 60-70 dungeons, I have noticed that AST and WHM have no issue with healing tank when there is a big pull, but SCH needs to heal more and they become out of mana alot faster then the other two healing classes. This could mean that the players playing the AST and WHM were just more compentent in healing then SCH that I have met or that SCH is just worse at healing compared to the other two classes.